Isolation and identification of Paenibacillus polymyxa strain and its control effect on Fusarium bulbigenum of sweet potato

【Objective】To screen Bacillus with antagonistic effect on Fusarium bulbigenum and provide strain resources for biological control of F. bulbigenum.【Method】Bacillus antagonistic to F. bulbigenum was screened from maize rhizosphere soil by plate antagonism method;classification and identification by biological characteristics and 16S rDNA sequence analysis;the control effect of isolated strains against F. bulbigenum was tested by pot experiment,and the effects of isolated strains on the contents of abscisic acid(ABA)and gibberellin(GA),the activities of superoxide dismutase(SOD) and peroxidase(POD) and soluble protein of sweet potato leaves were detected.【Result】A milky white strain with antagonistic effect was isolated from the rhizosphere soil of maize,named as HAAS05.Through 16S rDNA sequence analysis and phylogenetic tree analysis,HAAS05 strain was identified as Paenibacillus polymyxa.The biocontrol experiment of strain HAAS05 was carried out by pot experiment,and the hormone content,enzyme activity and soluble protein content of the tested plants were detected.The results of pot experiment showed that HAAS05 strain had obvious antagonistic effect on F. bulbigenum.After 10 d treatment with HAAS05 bacterial suspensions with OD_{600 nm}=0.20and OD_{600 nm}=0.40,the ABA content in sweet potato leaves was significantly lower than that in the treatment only inoculated with pathogens(201.94 ng/g)(P<0.05,the same below),which were 52.29 and 107.10 ng/g,respectively.The GA content was significantly higher than that in the treatment that only inoculated with pathogens(7.05 ng/g),which were8.10 and 10.31 ng/g,respectively.The SOD activity and soluble protein content in sweet potato leaves were significantly higher than those in the treatment only inoculated with pathogens.There was no significant change in the content of POD enzyme in the plant.【Conclusion】P.polymyxa HAAS05 has good biocontrol effect on F. bulbigenum and has certain application and development potential.